Method and device for extinguishing electrical arcs in circuit breakers



June 12, 1956 A. LATOUR METHOD AND DEVICE FOR EXTINGUISHING ELECTRICALARCS IN CIRCUIT BREAKERS 4 Sheets-Sheet 1 Filed June 8, 1953 INVENTOR.

Andr LATOUR Attorney June 12, 1956 A. L.ATOUR 2,750,476

METHOD AND DEVICE FOR EXTINGUISHING ELECTRICAL ARCS IN CIRCUIT BREAKERSFiled June 8, 1953 4 Sheets-Sheet 2 I rw- Fug. 2 Fig, 6 N.

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June 12, 1956 A. LATOUR METHOD AND DEVICE FOR EXTINGUISHING ELECTRICALARCS IN CIRCUIT BREAKERS 4 Sheets-Sheet. 3

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June 12, 1956 A. LATOUR METHOD AND DEVICE FOR EXTINGUISHING ELECTRICALARCS IN CIRCUIT BREAKERS 4 SheetsSheet 4 Filed June 8, 1953 INVENTOR.

LATOUR Andr BY Kama/1A MIAM RU Attorney Unite States Andre Latonr,Grenoble, France, assignor to Etablissemerits Merlin & Gerin, Grenoble,France Application June 8, 1953, Serial No. 360,299

Claims priority, application France October 13, 1949 Claims. ((31.208-147} This in a continuation in part of my earlier patentapplication, Serial Number 188,148, filed on October 3, 1950, now PatentNo. 2,668,890, issued February 9, 1954.

The invention refers to circuit breakers of the type in which the arc isdrawn between separable contact members contained in an arc formationchamber provided with means for expanding the are into and within an arcextinguishing chamber contiguous with the arc formation chamber.

More particularly, the invention relates to an are extinguishing chamberwhich includes at least two parallel plates of insulating material,spaced apart from each other to leave a narrow space therebetween anddisposed transversely of the direction of separation of the contacts orthe initial direction of the arc, and wherein conductive elements orpaths are provided in pairs diverging in V-form from each other andwhich draw the are or the arc in sections into the space or the spacesbetween the plates and turn the are or the are sections round into aposition substantially perpendicular to the initial path of the arc.

In the method of the invention, the arc is caused to turn transverselyof its initial direction into, and to expand within, the space betweentwo plates, or as divisional arcs within the spaces between more thantwo'plates of insulating material provided with conductive paths andarranged transversely of the direction of separation of the contactmembers between which the arc is initially drawn. However, while theroots of the arc or of the arc sections travel along the conductivepaths and approach the terminals of the conductive paths, thetransversal development and expansion of the are or its sections islimited to a fraction of the transversal extension of the space orspaces between the plates. Thereon, while the roots of the are or of itssections are held upon the terminals of the conductive paths, part-waysalong the plates, the arc is allowed, or its sections are allowed, todevelop and expand transversely and longitudinally of the plates to amultiple of the transversal extension of the space or spaces between theplates, the are or each one of its sections in the form of a nearlyannular loop within the space or spaces between the plates untilextinction.

In accordance with a further development of this method, the arc, underthe action of the electrodynamic forces, is allowed to develop and toexpand further within the space, or the divisional arcs within thespaces between adjacent plates, until the arc has, or the divisionalarcs have developed to a curve of an arcus of at least 1r, or, stillfurther, have reached a nearly closed annular form, preferably of anarcus of 3/21r or more and thereon extinguish within the spaces orspace.

In my U. S. patent application Serial Number 188,148, filed on October3, 1950, now U. S. Patent No. 2,668,890, I have described and claimed adevice for extinguishing an electric arc to be drawn between separablecontact members, a device which includes a set of at least two spacedparallel plates of insulating material disposed transversely of thedirection of separation of the contact members. These plates have ontheir faces conductive means atent O 2,750,476 Patented June 12, 1956disposed and adapted to draw the arc into the space or spaces betweenthe plates, turn it round into a position substantially parallel to theplates. The conductive means disposed on opposite faces of each platediverge relatively to each other and terminate within the space atintermediate points of the space. The are is thus drawn as a whole or insections into the space or spaces between the plates, turned round intoa position substantially parallel to the plates and caused to form aperipherally expanding loop within the space or peripherally expandingloops within the spaces.

The present invention has for its object arrangements of the insulatingplates and of the conductive elements carried by them which will allowthe arc loops to expand within the space or spaces between juxtaposed,consecutive plates from their roots peripherally to a loop of a lengthwhich is a multiple of the greatest distance between the conductiveelements, or to a nearly closed annular form of a multiple of the lengthof the opening angle between the electrodes from which the loops startto develop and to expand.

This expansion of the loops from their roots to curves of nearly closedannular form and of great length or arcs, and of generally circular oroblong form, within the loop developing spaces or chambers will resultin highly favor able de-ionizing conditions of the chambers and to rapidextinction of the loop or loops within the chamber or chambers.

An arc loop developing between given electrodes, starting from a shortflat are somewhat longer than the distance the roots, on their travel onpaths diverging from each other in V-form, reach in their farthestposition on the electrodes, will under the effect of the electrodynamicforces expand to a generally circular loop of a certain size. In orderto allow full expansion within the loop chamber of the loop or aresection, the conductive elements, in accordance with the invention, areso shaped and disposed that they end in the lower part of the spaces orloop chambers. The part of these spaces or chambers above the conductiveelements is so dimensioned that when the geometric center of that parti. e. the useful part, or the part of the plate against which the arcdevelops, is joined by imaginary radii to the nearest points or lateralupmost tips of the diverging edges of the conductive elements orelectrodes, these radii form an angle of an arcus less than 11' so thatwhen the roots of the loops have travelled to said points or tips, theloops may develop within the spaces to a curve of an arcus of at least11' or still further, to a nearly closed annular, generally circularcurve of an arcus greater than 3/ 211'. Preferably, the angle of theradii is equal to or even less than 1r/4, in such a manner that the loopmay develop to an arcus equal to or greater than 7/ 411-, allowing theshape of the loop to be almost circular.

With loops of such large size, the invention has for its object to holdthe transverse dimensions of the loop chambers in certain limits.

An arc loop freely developing between given electrodes, starting from ashort, flat arc, will, under the action of the electrodynamic forces,expand to a circular shape which for a given cutting power may actuallybe determined by the traces which the arc leaves on the faces of theinsulating plates.

For the purpose of reducing the lateral extension of the arcs, theinvention provides the plates laterally with marginal spacing memberswhich may be integral with the plates or mounted as keys in grooves ofthe plates, or be secured thereto by any other convenient orconventional means. The lateral spacing members will thus space apartfrom one another the consecutive plates and, seen in the direction inwhich the arc is originally drawn will provide between each pair ofjuxtaposed, consecutive plates of the stack or set a flat spaceand atthe same time will constitute the lateral closure walls of these spacesor chambers Within which the arc loop develops and expands.

In' order to reduce the width of the lateral extension of the-arc, inaccordance with this feature of the invention, the distance between thewalls, which laterally confine the are or loop developing and expandingspace, is made narrower than the trace of a loop of average powerindicates, so that a loop of average energy is compelled to take duringits expansion an elongated or oblong form along the lateral walls. Theplates will thus have their useful part in form of a rectangle, of awidth less than the mean diameter of the loops formed by the arc for thecutting power considered.

The conductive elements are shaped with two symmetric wings integrallyconnected by a bridge which is to straddle thelower edge of the plate,the wings on opposite faces ofthe plates and opposite wings of each loopchamber thus being'substantially symmetrically arranged withrespect tothe vertical median axes of the plates and of the loop chambers,respectively. The edges of each pairof wings'on opposite faces of theplates and, consequently, also of the pair on opposite faces of eachchamber, diverge in V -form relatively to each other.

In accordance with a further development of the invention, these lateralspacing members or walls which determine by their spacing thetransversal width of the loop developing and expanding chambers, mayalso hold the conductive elements firmly in position when they are of athickness equal to or slightly higher than that of the conductiveelements, so that when the plates are stacked together, adjacent plateshold or clamp between themselves the conductive elements of the enclosedspace against displacement.

When it is desirable to extend further the length to which the loops maybe drawn within the chambers, in accordance with another feature of theinvention, the plates may be provided with obstacles which compel theare to take a sinuate or meandrous path. This may be achieved byproviding additional, intermediate spacing members extended parallel tothe longitudinal axis of the plate and projecting into the loop chamber;or by providing the lateral walls of the chamber with points whichproject into the interior of the chamber and thus extend slightly thelength of the are.

In order to enhance the cooling effect of the plates through intimatecontact between arc loop and plate, in accordance with a further featureof the invention, the loop-may be laminated or spread out thinly byreducing between adjacent plates the width of the clearance within whichthe loop may develop and expand. This may be achieved by lesseningthrough increased thickness of certain parts of the plates the clearancewhich separates the plates, in such a manner that the loop whilepenetrating into this narrow clearance is flattened or laminated. Thusthe center portion of the space for developing and expanding the arc,the portion of the space above opposite conductive elements, may beraised above the'remaining surface so as to compel the arc loop toflatten out in this center portion.

To the same end, there may be inserted above the part left free for thedevelopment for the arc and between adjacent plates, a flame-arresterwhich on the one hand diminishes the cross-sectional area of the passageand thus compels a close contact between loop and plate and, on theother hand, presents with its lower edge a surface on which the arc loopmay abut while expanding in laminated form into the gaps betweenarrester-plate and. insulating plates. This edge may also be providedwith points of insulating material projecting into the loop chamber,with the advantage that the length of the loop is slightly augmented.

The invention is further concerned with a modification of the device bymeans of which an apparatus with sub-. stantially the same cuttingpower, the same space requirement, and the same type of insulatingplates furnished with conductive elements diverging in V-form, may beemployed as a circuit breaker for high voltage and lower amperage and asa circuit breaker for high amperage and correspondingly lower voltage.-

To this end, there are intercalated between the insulating platesfurnished with conductive paths unfurnished insulating plates. Theseunfurnished insulating plates are provided each with a notch extendedfrom the lower edge upwards, towards the upper part of the plate. Thesenotches are generally of wedge shape having their greatest width attheir lower part so as to given open space or passage to the loop as itdevelops between oposite and diverging conductive paths on furnishedinsulating plates which face each other and between which the notchedunfurnished insulating plates are intercalated or inserted.

In this way, the loop, while it develops and expands between twoconductive elements which face each other and diverge relatively to eachother, is divided into two half-loops, each of which is enclosed betweena pair of consecutive insulating plates, one furnished, the otherunfurnished. The cross-sectional area through which the hot gases,developed by the loop, escape, thus has been doubled without anyincrease of the distance or clearance between adjacent plates.

The amperage of the current to be interrupted may thus be increased tonearly the double compared with the arrangement where all the insulatingplates, spaced at this same distance, are furnished with conductivepaths while with the same requirement of space the number ofconvolution's of the helix which the are forms is reduced to one halfand accordingly the admissible voltage. The cutting power thus remainsunchanged.

These and other features of the invention will become apparent as thespecific description of the invention proceeds in which the inventionwill be described with reference to the accompanying drawings which formpart of this specification and which by way of example illustrate anembodiment of the invention. These drawings are to be understoodexplicative of the invention but not limitative of its scope. Otherembodiments incorporating the principle underlying my invention arefeasible without departing from the spirit and ambit of my appendedclaims.

In'the drawings:

Fig. l is, on a reduced scale and rather diagrammatically, alongitudinal section, partly along the middle plane, partly in frontthereof, of an embodiment of a circuit breaker'provided with arcsubdividing conductive elements with their insulating plates inaccordance with the invention;

Fig. 2 is a front view of an insulating plate of' the inventionfurnished with a conductive element;

Figs. 3 to 6 are cross-sections along the lines 3-3; 44; 5-5; and anelevational section along line 6-6' of Fig. 2, respectively;

Fig. 7 is an exploded, partly fractional view of two consecutiveinsulating plates furnished with conductive elements;

Fig. 8 is a longitudinal section, similar to that of Fig. l,

of a set of insulating plates furnished with conductive elementsalternating with unfurnished insulating plates as a modification of theembodiment of Figs. 1 to 7;

Fig. 9 is a front view, and

Fig. 10 an elevational section along line Ill-10 of Fig. 9 of anunfurnished insulating plate of this modification.

In Figs. 1 and 8 the fixed and movable contacts are respectivelyrepresented by 11 and 12'. The two contacts are located inside an arcformation chamber 13,- not shown here in detail.

In order to develop the ignited are more rapidly than the movement ofthe movable contact would allow, an arcing contact 15 may be placedWithin the arc formation chamber of insulating material. The arcingcontact 15 may be connected to the movable contact 12. A blow out coil16 may also be employed which may be connected to one of the terminals17 of the circuit breaker. The coil 16 acts upon the magnetic core 18the legs 19 of which enclose the arc formation chamber.

In the upper part of the circuit breaker, above the arc formationchamber, there is arranged a set of plates 21, transversely of thecontacts 11, 12 and 15, and in a space which constitutes the arcextinguishing chamber. The plates are of insulating material and areprovided at their lower edge with a cutout 22 over which the conductiveelement with its wings 23, 24 is bent and which it straddles with itsbridge 25, one wing 23 thus being in front, the other 24 in the rear ofthe appertaining insulating plate 21, as Figs. 2 to 7 illustrate.

The wings, at their inmost edges, where the arc loops start to develop,may be rectilinear as between 26 and 27 and their edges may then becurved, as at 28 so that conductive elements or wings on opposite facesof each plate and thus opposite elements in each space, betweenjuxtaposed, consecutive plates of the set, diverge in V- form relativelyto each other. In this way, the arc is drawn into the spaces between theplates, is turned round into a position parallel to the plates.Travelling along the curved edges 28 of the wings, the arc is caused toform peripherally expanding loops, or convolutions of a helix, in thespaces between successive furnished plates, successive positions of theloops being indicated in Fig. 2 by the broken lines a, b, c, d, e, f,and g.

The outer or lateral edges of the wings beyond their upmost lateral tipsA, B are extended freely downwards inside the spaces between consecutivefurnished plates as shown between the points 29, 30, Fig. 2, at adistance from the lateral spacing members or ribs 31, 32 by means ofwhich the plates 21 may be stacked together to a set, Fig. 1. Theselateral ribs or spacing members thus provide for a proper spacing of theplates to accommodate in the spaces therebetween the conductive elementsand allow the arc loops to develop and expand.

As Fig. 2 illustrates, the conductive elements, wings 23, 24 areextended from their lower edge, or the straddling bridge 25, into thespace or chamber between the plates and terminate in the lower partthereof. The part of the space above the conductive elements or the partof this space left free for the development of the loop, is sodimensioned that the imaginary radii from the geometric center C of thispart, that is of the part 33, 34, 35 and 36, to the lateral tips A, B ofthe diverging elements or wings 23, 24 form an angle less than 1r/2, inthe instance illustrated about 1r/4, or even a still smaller angle.Accordingly, when the roots of the loop have travelled to the tips A, B,the loops may develop within the space to a nearly closed annular formof an arcus greater than 3/21r, as the curves and g indicate.

In order to hold the transverse dimensions of the loop chamber incertain limits, the distance between the lateral spacing members orwalls 31, 32 will be made narrower than the width a freely expandingloop would occupy so that the loop is compelled to take an oblong formalong the lateral walls of the chamber, as likewise indicated by curves7 and g.

v The heights of the spacing members, as a rule, will be substantiallyequal to the thickness of the conductive element, which they hold on thefoot ledges 37, 38, as Figs. 1, and 6 illustrate. The plates, whenstacked together, thus leave a small clearance between themselves.

In order to produce an intimate contact between loop and plate, theclearance between adjacent plates may be reduced. In order thus toattenuate the loop and enhance the cooling effect of the insulatingplates, a portion 39 of the space for developing and expanding the arc,Figs. 2, 4, 6, may be raised above the remaining surface of the plate21, thus leaving a narrow clearance 40 between boss 39 and theconsecutive insulating plate 21.

To a. similar purpose, the plates may be provided at.

their top part with a flame-arrester 41 of insulating ma= terial. Thisflame-arrester is extended between the lateral spacing members 31, 32and may be held in'position by supplemental, intermediate spacingmembers 42, 43. The flame-arrester is of a thickness so as to leavenarrow clearances 44, 45', respectively, between arrester plate 41 andthe appertaining plate 21 and between arrester plate and the juxtaposed,consecutive insulating plate. The arc, if not priorly extinguished, willbe attenuated and effectively cooled and will thus be finallyextinguished and prevented from issuing as a flame from the top of theset of the plates.

In order to make possible a further extension of the length of the loopwithin the loop chamber, the plates may be provided with obstacles, suchas lateral, internally projecting points 48 at one or both of thelateral walls 31 or 32, points 49 at the internal ends of the spacingmembers 42, 43, which points compel the arc loops to take a meandrouspath, as illustrated by curve g.

Figs. 8 to 10 illustrate an arrangement for heavy currents, relativelyheavier than those for which the arrangement of Figs. 1 to 7 is to beemployed and for correspondingly lower voltages.

Insulating plates 21 furnished with conductive elements 23, 24, such asdescribed with reference to Figs. 2 to 7, are employed alternatinglywith unfurnished insulating plates 51. These unfurnished plates aregenerally of the same configuration as the furnished plates 21, they maybe provided with lateral spacing members or walls 31, 32, intermediate,longitudinally extended spacing members 42, 43, and with aflame-arrester 41 as described in detail with reference to Figs. 2 to 6.

The unfurnished plates 51, however, are distinguished through a notch52, 53, generally of wedge shape and extended from the lower edge of theinsulating plate upwards towards the upper part thereof, ending in afine point near the flame-arrester 41. The notch is Wide at its lowerpart 52 so as to give open space or access to the loop at the origin ofits formation. The loop thus is developed between a wing 23 to the rearof plate 51 and in front of the preceding furnished plate 21 and a Wing24 in front of plate 51 and to the rear of the succeeding plate 21, thetwo wings being indicated in broken lines. The wings are respectivelyseated on a foot ledge or spacing member 37 of the preceding plate and afoot ledge or spacing member 55 of the unfurnished plate 41.

By means of this arrangement, the are drawn between the plates 21 bymeans of the conductive elements and turned round in loops, orconvolutions of a helix, substantially parallel to the plates, will findfor each loophalf a separate space for development and expansion, eachloop-half enclosed between a furnished and an unfurnished plate with thecross-sectional area for the escape of the hot gases thus doubledwithout any increase of the narrow clearances through which the loopsare to expand and thus without any adverse effect on the cooling andextinguishing capacity of the apparatus.

1 claim:

1. In a device for extinguishing an electric arc to be drawn betweenseparable contact members, a set of at least two plates of insulatingmaterial disposed transversely of the direction of separation of saidcontact members, said plates having upon their faces conductive elementsstraddling the lower edges thereof, conductive elements on oppositefaces of each plate and opposite elements in each space betweenjuxtaposed consecutive plates of the set diverging in V-form relativelyto each other, thereby to draw the are into the spaces between saidplates, turn it round into a position substantially parallel to saidplates and cause the arc to form peripherally expanding loops in saidspaces; said conductive elements being extended from said lower edgeinto said spaces terminating in the lower part thereof, the part of thespaces above said elements being so dimensioned that the imaginary radiifrom the geometric center of said part to '7 the lateral tips of thediverging conductive elements form an angle less .than ,r so that whenthe roots of the "loops have travelled to said tips, the loops maydevelop within said spaces to a curve of an arcus greater than 1r.

2. A device as set forth in claim 1 wherein said angle is approximately1r/4. so that the loops may develop within said space .to a nearlyclosed curve of an arcus of approximately 7/ 41r.

3. In a device for extinguishing an electric arc to be drawn betweenseparable contact members. a set of at least two plates of insulatingmaterial disposed transversely of the direction of separation of thecontact members, said plates having upon their faces conductive elementsstraddling the lower edges thereof, conductive elements on oppositefaces of each plate and opposite elements in each space betweenjuxtaposed consecutive plates of the set divering in V-form relativelyto each other; thereby to draw the are into the spaces between theplates, turn it round into a position substantially parallel to saidplates and cause the arc to form peripherally expanding loops in saidspaces; said plates being provided with marginal spacing members forminglateral walls on the plates confining, when the plates are stackedtogether, laterally between juxtaposed, consecutive plates the loopdeveloping and expanding space, the distance between said lateral wallsbeing narrow so as to compel a loop of average energy to take during itsexpansion an oblong form along said lateral walls.

4. In a device for extinguishing an electric arc to be drawn betweenseparable contact members, a set of at least two plates of insulatingmaterial disposed transversely of the direction of separation of thecontact members, said plates having upon their faces conductive elementsstraddling the lower edges thereof, conductive elements on oppositefaces of each plate and opposite elements in each space betweenjuxtaposed consecutive plates of the set diverging in Vform relativelyto each other; thereby to draw the are into the spaces between theplates, turn it round into a position substantially parallel to saidplates and cause the arc to form peripherally expanding loops in saidspaces; said plates being provided with marginal spacing members forminglateral walls on the plates confining, when the plates are stackedtogether, laterally between juxtaposed consecutive plates the loopdeveloping and expanding space; said plates being further provided withmeans for reducing the clearance between juxtaposed plates.

5. A device as set forth in claim 4 wherein the center portion of theplate within the space for developing and expanding the loop is raisedabove the remaining surface of the plate thereby to produce an intimatecontact be tween loop and raised plate surface and enhance the coolingeffect of the plate.

6. A device as set forth in claim 4 wherein said plates comprise attheir top parts a flame-arrester plate of insulating material disposedand extended between said lateral spacing members, said arrester platesbeing of a thickness so as to leave a narrow clearance between eacharrester plate and its appertaining insulating plate and between saidarrester plate and the juxtaposed consecutive plate, thereby toattenuate the loop, enhance the cooling effect of the plates, extinguishthe are thus preventing the same from issuing as a flame from the top ofsaid set of plates.

7. In a device for extinguishing an electric arc to be drawn betweenseparable contact members, a set of at least two plates of insulatingmaterial disposed transversely of the direction of separation of thecontact members, said plates having upon their faces conductive elementsstraddling the lower edges thereof, conductive elements on oppositefaces of each plate and opposite elements in each space betweenjuxtaposed consecutive plates of the set diverging in V-form relativelyto each other; thereby to draw the are into the spaces between theplates, turn it round into a position substantially parallel to saidplates and cause the arc to form peripherally expanding loops in saidspaces; said plates being provided with marginal spacing members forminglateral walls on the plates confining, when the plates are stackedtogether, laterally between juxtaposed consecutive plates the loopdeveloping and expanding spaces, said plates being further provided withprojecting obstacles thereby to compel the arc loops to take meandrouspaths.

8. A device as set forth in claim 7 wherein said plates compriseintermediate supplementary spacing members extended parailel to thelongitudinal axis of each plate.

9. In a device for extinguishing an electric arc to be drawn betweenseparable contact members, a set of at least two plates of insulatingmaterial disposed transversely of the direction of separation of saidcontact memers, said plates having upon their faces conductive elementsstraddling the lower edges thereof, conductive elements on oppositefaces of each plate and opposite elements in each space betweenjuxtaposed consecutive plates of the set diverging in V-form relativelyto each other, thereby to draw the arc into the spaces between theplates, turn it round into a position substantially parallel to saidplates and cause the arc to form peripherally expanding loops in saidspaces; said plates being provided laterally with marginal spacingmembers, thereby to stack together the plates of said set and confine aslateral walls between adjacent plates said spaces for developing andexpanding the loops therein; said lateral walls being of a heightsubstantially equal to the thickness of said conductive elements so asfor the plates, when stacked together, to leave a small clearancebetween themselves.

10. In a device for extinguishing an electric arc to be drawn betweenseparable contact members, a set of plates of insulating materialdisposed transversely of the direction of separation of said contactmembers, alternate ones of said plates being furnished on their faceswith conductive elements straddling the lower edges thereof, conductiveelements of opposite faces of said alternate plates diverging in V-formrelatively to each other; the other unfurnished plates of said sethaving each a notch extended from the lower edge of said unfurnishedplates towards the upper part thereof, said notch being generally ofwedge shape, wide at its lower part so as to give open space to the loopat the origin of its formation between each other facing oppositeelements; said conductive elements being extended from said lower edgeupwards and ending in the lower parts of the spaces between adjacentones of said plates; thereby to draw the are between the plates, turn itround into a position substantially parallel to said plates, cause thearc to form peripherally expanding loops between said plates, eachloop-half in a separate space and each enclosed between a furnished andan unfurnished plate.

11. The method of extinguishing an electrical are between separablecontact members and at least two spaced parallel plates of insulatingmaterial arranged transversely of the direction of separation of saidcontact members and provided at their inside surfaces with conductiveopen-ended paths having their terminals partways along said plates; saidmethod including the steps of drawing the are, causing its roots totravel along said conductive paths and causing thereby the arc to turnround as a whole, transversely of its initial direction, causing theroots of the arc to travel along said conductive paths and, during thistravel and while the roots approach the terminals of said conductivepaths, limiting the transversal development and expansion of the arc toa fraction of the transversal extension of the space between saidplates, and, thereon, while the roots of the are are held upon saidterminals, part-ways along said plates, allowing further development andexpansion of the arc transversely and longitudinally of said plates andto a multiple of said transversal extension of the space between theplates and in the form of a nearly annular loop within the space betweensaid plates and parallel thereto until extinction.

12. The method of extinguishing an electrical are between separablecontact members and parallel plates of insulating material disposed inspaced relationship to one another and transversely of the direction ofseparation of said contact members and provided at their inside surfaceswith conductive open-ended paths having their terminals part-ways alongsaid plates; said method including the steps of drawing the arc, causingit to reach said conductive paths, thereby dividing said arc intoseveral sections, causing the roots of each section to travel along saidconductive paths and causing thereby each section as a whole to turnround, transversely of its initial direction, causing the roots of eacharc section to travel along said conductive paths and, during thistravel and while the roots approach the terminals of said conductivepaths, limiting the transversal development and expansion of each arcsection to a fraction of the transversal extension of the spaces betweensaid plates, and thereon, while the roots of the arc sections are heldupon said terminals, part-ways along said plates, allowing furtherdevelopment and expansion of each section transversely andlongitudinally of said plates and to a multiple of said transversalextension of the space between said plates and to a nearly annularconvolution of a helix into and within the space between adjacent onesof said plates and parallel thereto until extinction.

13. The method of extinguishing an electrical arc between separablecontact members and at least two spaced parallel plates of insulatingmaterial arranged transversely of the direction of separation of saidcontact members and provided at their inside surfaces with conductiveopenended paths having their terminals part-ways along said plates andnear to the entrance into the space between said plates; said methodincluding the steps of drawing the arc, causing its roots to travelalong said conductive paths and causing thereby the arc to turn round asa whole, transversely of its initial direction, causing the roots of thearc to travel along said conductive paths and, during this travel andwhile the roots approach the terminals of said conductive paths,limiting the transversal development and expansion of the arc to afraction of the transversal extension of the space between said plates,and, thereon, while the roots of the are are held upon said terminals,part-ways along said plates and near to the entrance into said space,allowing further development and expansion of the arc, under the actionof the electrodynamic forces within said space, transversely andlongitudinally of the plates and to a multiple of said transversalextension of the space between the plates until the arc has reached anearly closed annular form and thereon extinguishes.

14. The method of extinguishing an electrical are between separablecontact members and parallel plates of insulating material disposed inspaced relationship to one another and transversely of the direction ofseparation of said contact members and provided at their inside surfaceswith conductive open-ended paths having their terminals part-ways alongsaid plates and near to the entrance into the spaces between saidplates; said method including the steps of drawing the are, causing itto reach said conductive paths, thereby dividing it into severalsections, causing the roots of each section to travel along saidconductive paths and causing thereby each section to turn round as awhole, transversely of its initial direction, causing the roots of eacharc section to travel along said conductive paths and, during thistravel and While the roots approach the terminals of said conductivepaths, limiting the traversal development and expansion of each arcsection to a fraction of the transversal extension of the spaces betweenthe plates, and, thereon, while the roots of the arc sections are heldupon said terminals, part-ways along said plates and near to theentrance of each one of said spaces, allowing further development andexpansion of each arc section, under the action of the electrodynamicforces, transversely and longitudinally of said plates and to a multipleof said transversal extension of the spaces between the plates andwithin said space, parallel to said plates, until each arc section hasreached a nearly closed annular form of an arena of at least 3/21r andthereon extinguishes.

15. The method of extinguishing an electrical are between separablecontact members and a set of spaced parallel plates of insulatedmaterial arranged transversely of the direction of separation of saidcontact members and furnished at their surfaces with conductiveopen-ended paths having their terminals part-ways along said plates,unfurnished plates being intercalated between said furnished plates,furnished and unfurnished plates thus alternating with one another andproviding separate spaces, each of said spaces being constituted by afurnished and unfurnished plate in juxtaposition, said unfurnishedplates having a notch extended from the lower edge to the upper partthereof, said notch being generally of wedge shape, wide at its lowerpart; said method including the steps of, after having drawn the arc,causing it to reach said conductive paths, thereby dividing the arc intoseveral sections, causing the roots of each section to travel along saidconductive paths and causing thereby each section as a whole to turnround, transversely of its initial direction, causing the roots of eacharc section to travel along said conductive paths and, during thistravel and while the roots approach the terminals of the conductivepaths, limiting the transversal development and expansion of each arcsection to a fraction of the transversal extension of the spaces betweenthe plates, and, thereon, while the roots are held upon said terminals,part-ways along said plates, allowing further development and expansionof the arc sections, transversely and longitudinally of said plates andto a multiple of said transversal extension of the spaces between theplates, each section in the form of a nearly annular loop with eachloop-half in one of said separate spaces, the loops at the origin oftheir formation passing through said notches.

References Cited in the file of this patent UNITED STATES PATENTS2,436,189 Boehne Feb. 17, 1948 2,564,178 Strobel Aug. 14, 1951 FOREIGNPATENTS 253,098 Switzerland Nov. 1, 1948

